Stunning of animals such as pigs and chicken with high concentration of CO2 is debated by scientists and in the media. There is a general consensus that the method of group-wise CO2-stunning is the best method available up until the actual stunning. An aversive reaction may occur in the animals prior to stunning. The aversive reaction includes un-resting and/or panic-like behavior among the animals. The aversive reaction lasts 10-30 seconds, and this is the only part of the process that is subject to a quite rigorous debate. CO2-stunning is close to ideal concerning handling of living animals, and concerning the quality of the stunning, and concerning meat quality such as reduced drip-loss and hemorrhages, when performed according to the recommendations. No other stunning methods perform nearly as well as CO2-stunning. Most high capacity slaughter houses use CO2-stunning.
At abattoirs pigs must be stunned in a quick stunning process e.g. by exposure to CO2 where high concentration of CO2 of above 60% secure a quick stunning process, however most of such pigs show aversive reactions.
The present invention relates to a method to avoid or relieve the aversive reaction to the high CO2-concentrations, and with a correctly performed group wise CO2-stunning a method including pre-stunning and final-stunning would be a close to perfect method concerning animal welfare and meat quality e.g. reduced drip loss and hemorrhages. The present invention may also be performed as an integrated part of the stunning process.
The pre-stunning step e.g. performed as an integrated part of the stunning process is also believed to contribute to the reduction of muscle hemorrhages in ham and tenderloins, that are considered a significant source of economic loss by the slaughterhouse industry.
DE102008003865 describes pre-stunning and final-stunning of pigs by guiding pigs into a chamber filled with inert gas such as argon for pre-stunning, and conveying the pigs further into another chamber filled with carbon-di-oxide for final-stunning and where the pigs hang with head down during the final-stunning. This pre-stunning of pigs is different than the present invention. It is undesirable to manage pigs during the stunning process such that operators suspend the pigs, as this includes burdensome working positions for the operators.
WO 98/31231 (‘A procedure and equipment for treating poultry before slaughter’) and WO 99/60861 (‘A method and equipment for the production of a gas mixture’) describe a procedure and equipment for the treatment, such as anaesthetisation or killing, of poultry by using gas. The gas comprises oxygen and carbon dioxide, among other components. The concentration of carbon dioxide is increased either continuously or discontinuously. In the equipment the poultry are exposed to the gas in a chamber, that may comprise a belt conveyer and further be separated into three treatment zones.
WO 94/15469 (‘Method and device for stunning of poultry’) describes a method and device for stunning of poultry, which poultry are taken into a first chamber to contain a first stunning gas or gas mixture, and the poultry are subsequently taken into a second chamber which is essentially separated from the first chamber as regards gas and which contains a second stunning gas or gas mixture for increasing the stunning achieved in the first chamber. The oxygen concentration may in the first chamber be at least 15% by vol. Preferably, the stunning gas in this case comprises carbon dioxide in a concentration of at least 25% by vol., but nitrous oxide, ether, cyclopropane or halothane can also be used as the stunning gas.
WO 01/91563 (‘Method and apparatus for at least stunning an animal for slaughter’) relates to a method for at least stunning an animal for slaughter, comprising two processing steps of: a) reducing the consciousness of the animal for slaughter using a gas, and b) administering to the animal for slaughter with reduced consciousness at least one electrical pulse in order to influence the heart function of the animal for slaughter. The invention also relates to an apparatus for at least stunning an animal for slaughter, comprising: a gas stunning space with means for gas feed, and electrical stunning means. The stunning gas comprises at least 30% CO2.
None of the described prior-art methods use a combination of CO2, O2 and N2O for a pre-stunning or stunning process.
In the stunning method described herein which includes a pre-stunning step the animals are handled as little as possible by operators to avoid stressing the animals while they are conscious.